Electronic devices which comprise organic, organometallic and/or polymeric semiconductors are being used ever more frequently in commercial products or are just about to be introduced onto the market. Examples which may be mentioned here are organic-based charge-transport materials (in general triarylamine-based hole transporters) in photocopiers and organic or polymeric light-emitting diodes (OLEDs or PLEDs) in display devices or organic photoreceptors in copiers. Organic solar cells (O-SCs), organic field-effect transistors (O-FETs), organic thin-film transistors (O-TFTs), organic integrated circuits (O-ICs), organic optical amplifiers or organic laser diodes (O-lasers) are also at an advanced stage of development and may achieve major importance in the future.
Many of these electronic and opto-electronic devices have, irrespective of the particular application, the following general layer structure, which can be adapted to the particular application:                (1) substrate,        (2) electrode, frequently metallic or inorganic, but also made from organic or polymeric conductive materials;        (3) charge-injection layer or interlayer for compensation of unevenness of the electrode (“planarisation layer”), frequently made from a conductive, doped polymer,        (4) organic semiconductors,        (5) possibly a further charge-transport or charge-injection or charge-blocking layer,        (6) counterelectrode, materials as mentioned under (2),        (7) encapsulation.        
The above arrangement represents the general structure of an opto-electronic device, where various layers can be combined, so that, in the simplest case, an arrangement comprising two electrodes, between which an organic layer is located, results. The organic layer in this case fulfils all functions, including the emission of light. A system of this type is described, for example, in WO 9013148 A1 based on poly(p-phenylenes).
A problem which arises in a “three-layer system” of this type is, however, the lack of a possibility to optimise the individual constituents in different layers with respect to their properties, as is solved easily, for example, in the case of SMOLEDs (“small-molecule OLEDs”) through a multilayered structure. A “small molecule OLED” consists, for example, of one or more organic hole-injection layers, hole-transport layers, emission layers, electron-transport layers and electron-injection layers as well as an anode and a cathode, where the entire system is usually located on a glass substrate. An advantage of a multilayered structure of this type consists in that various functions of charge injection, charge transport and emission can be divided into the various layers and the properties of the respective layers can thus be modified separately.
The layers in SMOLED devices are usually applied by vapour deposition in a vacuum chamber. However, this process is complex and thus expensive and is unsuitable, in particular, for large molecules, such as, for example, polymers, but also for many small molecules, which frequently decompose under the vapour-deposition conditions.
The application of layers from solution is therefore advantageous, where both small molecules and also oligomers or polymers can be processed from solution.
In the conventional process for OLED production, both by deposition from the gas phase or solution-processed, it is difficult to control the distribution of the individual components. The components are usually distributed randomly. This is undesired for some physical properties of such systems, for example in the case of so-called “double doping” in triplet systems (see Kawamura, Y.; Yanagida, S.; Forrest, S. R., “Energy transfer in polymer electro phosphorescent light emitting device with single and multiple doped luminescent layers”, J. Appl. Phys., 92 (1), 87-93, 2002). It is reported therein that a very efficient polymer (PHOLED) is produced by using poly(9-vinylcarabazole) (PVK) as host molecule, which is doped with one or more phosphorescent cyclometallated Ir(III) complexes. It is usually assumed that energy transfer, for example by the Förster mechanism, takes place in the case of double doping.
The Förster energy transfer rate ΓDA can be represented theoretically, for example, by the following formula:ΓDA∝1/R6,where R represents the separation between donor and acceptor. This separation is usually also known as the Förster radius. In order to facilitate efficient energy transfer, for example by Förster energy transfer or others, it is thus necessary to position the donor and acceptor, i.e. the two emitter compounds or metal complexes, as close as possible, advantageously within the so-called Förster radius.
The fact that the two emitters are usually distributed randomly means that the requisite small separation of the two emitter molecules from one another (donor and acceptor) is not guaranteed to the full extent.